Chemical trace gas analysis in cleanrooms is a necessity in order to identify possible contaminations in good time and to detect the sources thereof. Until now, a number of methods have been used in cleanrooms (e.g., in semiconductor manufacturing) for the trace gas analysis.
In a first example, collection vessels are put up and, after a certain time of exposure in the cleanroom, the built-up concentration is evaluated by chemical/physical analysis, for example, by means of atomic absorption spectroscopy (AAS), gas chromatography (GC), inductively coupled plasma mass spectrometry (ICP-MS).
In a second example, use is made of individually put-up gas sensors and the corresponding signals thereof are evaluated. Such a method is known, e.g., from the article “Spatial and Temporal Distributions of a Gaseous Pollutant During Simulated Preventive Maintenance and Piping Leaking Events in a Working Cleanroom” by Shih-Hsuan Huang, et al., IEEE Transactions on Semiconductor Manufacturing, volume 22, number 3, August 2009. Here, mobile FTIR spectrometers (FTIR=“Fourier transform infrared spectrometer” or “Fourier transformation infrared spectrometer”) are used in the cleanroom for the gas measurement.
It is disadvantageous that the first method does not permit a fine resolution in time, since the concentration is built up integrated over time. Furthermore, the possible spatial resolution is restricted in the first example because the network of assembly points cannot be selected to be arbitrarily dense or because some points in the cleanroom are simply inaccessible, for example, the space above a manufacturing plant. This restriction largely also applies to the individually put-up gas sensors in the second example. Further disadvantages include cross contaminations, which are caused by handling the analytic instruments themselves during both the mentioned examples.